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INVESTIGATION OF TRANSFER OF FLUORESCENT TRACERS FROM SURFACES TO SKIN
Citation:
Kissel, J. C., R. Showlund, J. H. Shirai, J C. Suggs, AND E A. CohenHubal. INVESTIGATION OF TRANSFER OF FLUORESCENT TRACERS FROM SURFACES TO SKIN. Presented at International Sociey of Exposure Analysis 2002 Conference, Vancouver, Canada, August 11-15, 2002.
Impact/Purpose:
The primary objective of this research project is to develop a scientifically-robust, complete multimedia, multi-pathway human exposure source-to-dose modeling system with modules and computational tools that can estimate exposures and doses to the general population, as well as to identifiable susceptible subpopulations, and can predict and diagnose the complex relationships which exist between source and exposure and dose -- and to ensure that this scientifically sound model, with its associated tools and the various modules included within, meets the needs of Program Offices and the scientific community for conducting risk assessments.
Description:
Under the provisions of the Food Quality Protection Act (FQPA), aggregate exposure assessments must be conducted for pesticides proposed for registration. Many aspects of dermal exposure assessment remain poorly quantified. For purposes of assessing surface-to-skin transfers relevant to FQPA, a series of trials have been conducted using fluorescent tracers as surrogates for pesticides. In these trials, adult volunteers contacted surfaces loaded with tracers with their fingertips. Factors investigated included contact duration, contact pressure, surface tracer loading, surface type, contact scenario, skin moisture, and tracer aqueous solubility. Each variable was limited to two possible states. A hand press station (force plate) linked to a personal computer was utilized to control and record duration and pressure. Target conditions for those variables were 3 or 10 seconds and 30 or 100 g/cm2. Initial average tracer surface loadings were 0.2 or 0.5 ug/cm2. Alternative surfaces were glass and a textured vinyl fabric. Contact was either static (press) or dynamic (swipe). Skin moisture on pre-moistened or dry fingers was assayed with a corneometer. One relatively hydrophilic and one relatively hydrophobic tracer were utilized. Digital images of both the fingers and the surfaces were captured under UV illumination before and after activity to attempt assessment of mass balance. Tracer loading vs. fluorescence calibration curves were produced for each individual volunteer to minimize potential effects of varying skin tones. Based on finger imaging, transfers of 0-1.5 ug of tracer to roughly 2-3 cm2 of finger surface were observed. Analysis of the relative importance of the experimental variables by multi-factorial anova is currently underway.
This work has been funded wholly or in part by the United States Environmental Protection Agency under contract no. 0D-5232-NTEX to the University of Washington. It has been subjected to Agency review and approved for publication.